Hydraulic cylinder device

ABSTRACT

A pair of hydraulic cylinders  10  which are coupled to a driven member, placed parallel to each other and extend/contract in synchronization with each other, and a control valve  20  which controls hydraulic fluid supplied to or discharged from the hydraulic cylinder  10  are provided. An elastic support mechanism  50  which supports the control valve  20  to each hydraulic cylinder between the paired hydraulic cylinders  10 ; metallic piping  30  and the metallic piping  40  which connect the control valve  20  with the respective hydraulic cylinders  10  and leads the hydraulic fluid controlled by the controlling valve  20 ; and curved portions  31   c   , 32, 41   c   , 42   a  which are provided at some midpoints of the piping and flexibly deform in accordance with relative deformation of each hydraulic cylinder  10  are provided. A difference in relative displacement of each hydraulic cylinder with respect to the control valve  20  is absorbed by deformation produced in the elastic support mechanism  50  and the curved portions.

FIELD OF THE INVENTION

This invention relates to an improvement in a hydraulic cylinderapparatus for driving a boom of heavy-duty machinery for construction,for example.

RELATED ART

Conventionally, for example, as disclosed in Japanese unexamined patentpublication 2002-21114, such a type of hydraulic cylinder apparatus isstructured such that a hydraulic cylinder is connected to a flexiblehose or the like provided for supplying and discharging hydraulic fluidand the flexible hose extends along a boom of the heavy-dutymachine/vehicle or the like in such a way as to be movable in accordancewith the movement of the boom or the like.

However, in such a hydraulic cylinder apparatus, if the flexible hosefor supplying the hydraulic fluid to the hydraulic cylinder is damaged,leakage of the hydraulic fluid makes it impossible for the hydrauliccylinder to bear a load on the boom or the like of the heavy-dutymachine/vehicle which thus causes a fall of the boom.

To prevent leakage of the oil for the hydraulic cylinder when theflexible hose is damaged, it is necessary to provide a check valve orthe like to the hydraulic cylinder for the prevention of such a fall.

Alternatively, instead of having the flexible hose connected to thehydraulic cylinder, a possible idea is the use of metallic piping thatis less liable to damage. However, because metallic piping has noflexibility, when the hydraulic cylinders produce relative displacementin accordance with deformation or movement of the boom, distortion maypossibly occur in the metallic piping connecting each hydraulic cylinderwith a control valve. In particular, in the case where two hydrauliccylinders are used to drive one boom and the metallic piping connectedto one control valve is divided along the way into two branchesconnected respectively to the hydraulic cylinders, if relativedisplacement between the two hydraulic cylinders occurs, the level ofdistortion on the metallic piping is increased and thus a crack maypossibly occur.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to prevent to the utmost theoccurrence of stress due to distortion on metallic piping connecting ahydraulic cylinder with a control valve.

It is also an object of the present invention to inhibit action of ahigh degree of distortion stress on metallic piping even when themetallic piping divided into branches along the way from a singlecontrol valve is connected to, particularly, a pair of hydrauliccylinders which are apt to produce relative displacement.

The present invention provides a hydraulic cylinder apparatus that isprovided with: a pair of hydraulic cylinders which are coupled to adriven member, placed parallel to each other and extend/contract insynchronization with each other; a control valve which controlshydraulic fluid supplied to or discharged from the pair of the hydrauliccylinders; an elastic support mechanism which supports the control valveto each hydraulic cylinder between the pair of the hydraulic cylinders;metallic piping which connects the control valve with each of the pairof the hydraulic cylinders and leads the hydraulic fluid controlled bythe control valve; and curved portions which are provided at somemidpoints of the piping and flexibly deform in accordance with relativedeformation of each of the pair of the hydraulic cylinders, whereby adifference in relative displacement of each of the pair of the hydrauliccylinders with respect to the control valve is absorbed.

Accordingly, in the present invention, the control valve and the pair ofthe hydraulic cylinders are connected by the use of metallic piping.Hence, high resistance to high pressure is ensured. Further, even whenthe pair of the hydraulic cylinders follow the movement or displacementin a direction in which the driven member is twisted, and thus producerelative displacement with each other, the difference in relativedisplacement between each of the pair of the hydraulic cylinders and thecontrol valve is absorbed by means of elastic deformation produced inthe elastic support mechanism and also of flexible deformation producedin each curved portion of the metallic piping. Thus, it is possible toreliably prevent the metallic piping from being damaged without actionof any undue force on the metallic piping.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a heavy-duty machine/vehicle illustrating anembodiment of the present invention.

FIG. 2 is a side view of the heavy-duty machine/vehicle ditto.

FIG. 3 is a front view of a pair of hydraulic cylinder apparatusesditto.

FIG. 4 is a rear view of the hydraulic cylinder apparatuses ditto.

FIG. 5 is a side view of the hydraulic cylinder apparatus ditto.

FIG. 6 is a plan view of the hydraulic cylinder apparatuses ditto whenviewed from above.

FIG. 7 is a plan view of the hydraulic cylinder apparatuses ditto whenviewed from below.

FIG. 8 is a sectional view of an elastic support mechanism ditto.

FIG. 9 is a hydraulic circuit diagram ditto.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment according to the present invention will be described belowwith reference to the accompanying drawings.

As shown in FIGS. 1 and 2, a heavy-duty machine/vehicle 1 forconstruction includes a machine/vehicle main-body 2 that turns on ahorizontal surface. A boom 3 is coupled to the front portion of themachine/vehicle main-body 2 in such a way as to be capable of beingswung onto a vertical surface. A pair of hydraulic cylinders 10, whichwill be described in detail later, is provided for driving the boom 3.An arm 4 is coupled to the leading end of the boom 3 in such a way as tobe capable of being swung, and driven by a single hydraulic cylinder 9.A bucket 5 is coupled to the leading end of the arm 4 in such a way asto be capable of being swung, and driven by a single hydraulic cylinder8.

The machine/vehicle main-body 2 is equipped with a hydraulic pressuresource unit, which is not shown in FIGS. 1 and 2. High pressurehydraulic fluid led from the hydraulic pressure source unit is suppliedto each of the hydraulic cylinders 8 to 10 so as to allow the operationof extending or contracting the cylinder. An operator manipulating themachine/vehicle 1 operates the hydraulic cylinders 8 to 10 for theextension/contraction movement to move the bucket 5, the arm 4 and theboom 3 for the excavation of earth or the carrying of soil and sand.

The aforementioned paired hydraulic cylinders 10 are located on bothsides of the boom 3 so as to hold it from the right and left sides. Eachof the hydraulic cylinders 10 moves a piston rod 12 with respect to acylinder tube 11 for the extension/contraction operation when hydraulicpressure is supplied to a piston which is not shown in the Figures. Thebase end of each cylinder tube 11 is coupled to the front portion of themachine/vehicle main-body 2 through a support shaft 13 in such a way asto be capable of being swung. The tip end of each piston rod 12 iscoupled to the corresponding side of the boom 3 through a support shaft14. Thus, the boom 3 turns upward when the hydraulic cylinder 10extends, and turns downward when the hydraulic cylinder 10 contracts.

A control valve 20 is located between and attached to the two hydrauliccylinders 10 driving the boom 3. The hydraulic cylinders 10 are operatedfor extension/contraction in synchronization with each other by thehydraulic fluid which is supplied from and discharged to the hydraulicpressure source through the control valve 20.

As illustrated in FIG. 3 to FIG. 7, the control valve 20 placed betweenthe two hydraulic cylinders 10 is mounted on a base plate 60 providedbetween the cylinder tubes 11, in a position below the boom 3.

The base plate 60 is supported by being coupled to both the hydraulictubes 11 via four elastic support mechanisms 50 which are located on thefour corners thereof.

First, the elastic support mechanism 50 will be described. Asillustrated in FIG. 8, the elastic support mechanism 50 includes: a band51 that is wound around the cylinder tube 11 of the hydraulic cylinder10; a sleeve 52 and a washer 55 that are tightly secured via a bolt 53and a nut 54 to the band 51; a hole 56 formed in the base plate 60 forthe sleeve 52 passing through there; and a bush 57 that is made of anelastic material such as rubber and interposed between the sleeve 52 andthe base plate 60.

The band 51 includes a pair of semi-ring-shaped band members 58 and 59,and a pair of bolts 49 for securely fastening respective ends of theband members 58 and 59 together. The band 51 is detachably wound on theouter peripheral face of the cylinder tube 11 of the hydraulic cylinder10. The band member 58 is welded to a support arm 48. The bolt 53 isinserted into the support arm 48.

The bush 57 has a cylindrical-shaped tube portion 57 a interposedbetween the sleeve 52 and the hole 56, and a disc-shaped flange portion57 b interposed between the support member 48 and the base plate 60. Thetube portion 57 a and the flange portion 57 b are formed in one piece ofelastic material such as rubber. Thereby, if relative displacement isproduced between the two hydraulic cylinders 10, the displacement isabsorbed so as to prevent deformation of the base plate 60.

The base plate 60 is attached to a rear face 60 b which is a reverseside of the base plate 60 in the front-rear direction of the vehiclebody. The base plate 60 serves the function of a protective member forpreventing the control valve 20 from suffering the impact of anobstruction.

The control valve 20 and the pair of hydraulic cylinders are connectedthrough metallic piping 30 and 40. The metallic piping 30 and themetallic piping 40 have a piping strength higher than that of a flexiblehose or the like, and adequate resistance to high pressure.

With the control valve 20 as the center, the metallic piping 30 and themetallic piping 40 are in symmetrical formation with respect to thecenter line Q between the paired hydraulic cylinders 10 as shown in FIG.3. Thereby, the hydraulic fluid flows equally from the control valve 20to each of the hydraulic cylinders 10 to allow the hydraulic cylinders10 to be operated in synchronization with each other.

The metallic piping 30 is provided for forming a connection between thecontrol valve 20 and the hydraulic chamber of the piston rod of eachhydraulic cylinder 10. The metallic piping 30 includes a single basepipe 32 connected via a connector 36 to the control valve 20, twoL-shaped branch pipes 31 each connected via a connector 35 to theleading end of each cylinder tube 11, and a T-shaped connector 33 forconnecting the base pipe 32 with the branch pipes 31.

The base pipe 32 extents such that the two ends thereof respectivelyconnected to the connectors 33 and 36 are at right angles to each otherto provide a curved portion 32 a between the ends. The curved portion 32a flexibly deforms, whereby the difference in relative displacement ofthe base plate 60 with respect to each hydraulic cylinder 10 isabsorbed.

Each of the L-shaped branch pipes 31 is composed of a pipe 31 aextending along the cylinder tube 11, a pipe 31 b extending at rightangles to the cylinder tube 11, and a curved portion 31 c connecting thepipe 31 a and the pipe 31 b. The curved portion 31 c flexibly deforms,whereby the difference in relative displacement of each hydrauliccylinder 10 is absorbed.

In this connection, the curved portion 32 a of the base pipe 32 and thecurved portion 31 c of the branch pipe 31 are both curved within anapproximate right angle range and also on the surfaces forming rightangles with each other. As a result of the foregoing, the absorption ofdistortion in three dimensional directions is achieved.

The metallic piping 4 b is provided for forming a connection between thecontrol valve 20 and the hydraulic chamber in the end of each hydrauliccylinder 10. The metallic piping 40 includes a single U-shaped base pipe42 connected via a connector 46 to the control valve 20, two L-shapedbranch pipes 41 each connected via a connector 45 to the base end ofeach cylinder tube 11, and a T-shaped connector 43 provided forconnecting the base pipe 42 with the branch pipes 41.

The base pipe 42 has two ends 42 b and 42 c respectively connected tothe connectors 43 and 46, and a curved portion 42 a forming a connectionbetween the ends 42 b and 42 c. In this case, the ends 42 b and 42 c ofthe U-shaped base pipe 42 extend parallel to each other on both sides ofthe base plate 60 so that the curved portion 42 a is curved in an arcshape to form a U shape around the end of the base plate 60. The curbedportion 42 a flexibly deforms, whereby the difference in relativedisplacement of the base plate 60 with respect to each hydrauliccylinder 10 is absorbed.

The branch pipe 41 is composed of a pipe 41 a extending along thecylinder tube 11, a pipe 41 b extending at right angles to the cylindertube 11, and a curved portion 41 c connecting the pipe 41 a and the pipe41 b. The curved portion 41 c flexibly deforms, whereby the differencein relative displacement of each hydraulic cylinder 10 is absorbed.

In this case, the curved portion 42 a of the base pipe 42 and the curvedportion 41 c of the branch pipe 41 are also curved on the surfaces atright angles to each other. Thereby, absorption of distortion in threedimensional directions is achieved.

The control valve 20 is located closer to the end-side end 11 b of eachcylinder tube 11 than the piston-rod-side end 11 a thereof. The portionof the metallic piping 30 close to the piston rod of the cylinder tube11 is longer in pipe length than the portion of the metallic piping 40close to the end of the cylinder tube 11.

As illustrated in the hydraulic circuit in FIG. 9, the control valve 20includes four flow control valves 21 a connected in a bridge circuit. Asupply passage 23 and a return passage 25 are connected selectively toeach of the hydraulic chambers of the pair of hydraulic cylinders 10 forextension/contraction operation of the hydraulic cylinders 10. Thesupply passage 23 intercommunicates with a hydraulic pump 22′, and thereturn passage 25 intercommunicates with a reservoir 24.

Likewise, the hydraulic cylinder 9 for driving the arm 4 is equippedwith a control valve including four flow control valves 21 b.

In the control valve 20, the degree of valve opening of each of the flowcontrol valves 21 a is controlled by a drive current sent from a controlunit which is not shown in the Figures. Through this control, the amountof the hydraulic fluid supplied to or discharged from each of thehydraulic chambers of the hydraulic cylinders 10 is controlled tothereby adjust the speed of extension or contraction of the hydrauliccylinders 10. If each of the flow control valves 21 a is fully closed orif the flow control valve that is connected to the hydraulic chamber ofthe hydraulic cylinder 10 under load is fully closed, outflow of thehydraulic fluid from the hydraulic cylinder 10 can be stopped to preventthe falling of the boom 3 due to the load.

In this case, out of the metallic piping 30 and the metallic piping 40which connect the control valve 20 and the hydraulic cylinders 10, highpressure acts specially on the metallic piping 40. However, it is stillpossible for the metallic piping 40 to provide adequate resistance topressure, unlike the case of a flexible tube.

In the foregoing structure, the operation will be described next.

The control valve 20 switches between supply and discharge of thehydraulic fluid to and from each hydraulic cylinder 10 to allow thehydraulic cylinders 10 to extend/contract in synchronization with eachother, and also the control valve 20 serves the function as an emergencyshutoff valve for holding the boom 3 in a lifted position to prevent itsfalling by means of stopping the outflow of the hydraulic fluid from thehydraulic cylinders 10.

The metallic piping 30 and the metallic piping 40 are used for forming ahydraulic pressure passage connecting the control valve 20 and each ofthe hydraulic chambers of the pair of hydraulic cylinders 10, therebymaking it possible to ensure adequate strength to withstand highpressure.

However, since the metallic piping 30 and the metallic piping 40 have noelasticity as a flexible tube does, the metallic piping has a lowcapability of absorbing stress caused by deformation or distortion. Inparticular, the two hydraulic cylinders 10 driving the boom 3 producerelative displacement following the deformation or movement in thedirection in which the boom 3 is twisted. Hence, distortion occurs inthe metallic piping 30 and the metallic piping 40 connecting the controlvalve and each hydraulic cylinder 10. However, the difference in therelative displacement of the control valve 20 with respect to eachhydraulic cylinder 10 is absorbed by elastic deformation of the bush 57of each elastic support mechanism 50, and also by flexible deformationof the curved portions 31 c and 32 a of the metallic piping 30 on thesurfaces at right angles to each other and flexible deformation of thecurved portions 41 c and 42 a of the metallic piping 40 on the surfacesat right angles to each other. Thus, it is possible to prevent damagecaused by distortion without the application of any undue force to themetallic piping 30 and the metallic piping 40.

Because the metallic. piping 40 has the curved portion 42 a of the basepipe 42 semi-circularly curving around the base plate 60, the metallicpiping 40 has a large amount of flexible deformability. Hence, thedifference in relative displacement of the base plate 60 with respect toeach hydraulic cylinder 10 is satisfactorily absorbed to make itpossible to prevent breakage of the piping.

The relative displacement caused following the deformation or movementof the boom 3 is larger at the rod-side end 11 a of the cylinder tube 11located close to the boom than that at the end-side end 11 b. Regardlessof the large relative displacement, however, the warp angle occurring onthe piping 30 is small and also the stress produced is low. This isbecause the control valve 20 is located closer to the end-side end 11 bof each cylinder tube 11 than the rod-side end 11 a, so that themetallic piping 30 is greater in pipe length than the metallic piping40.

It is obvious that the present invention is not limited to the foregoingembodiment, and various changes can be made within the scope of thetechnical idea. For example, the control valve 20 is mounted on the baseplate 60, but the control valve 20 can be supported directly by theelastic support mechanism 51.

INDUSTRIAL APPLICABILITY

The present invention is applicable as a hydraulic cylinder apparatusfor industrial machinery.

1. A hydraulic cylinder apparatus, comprising: a pair of hydrauliccylinders that are coupled to a driven member, are placed parallel toeach other, and extent/contract in synchronization with each other; acontrol valve that controls supply/discharge of hydraulic fluid from/tothe pair of the hydraulic cylinders; an elastic support mechanism thatsupports the control valve to each of the pair of the hydrauliccylinders between the pair of the hydraulic cylinders; metallic pipingthat connects the control valve and each of the pair of the hydrauliccylinders and leads hydraulic fluid controlled by the control valve; andcurved portions that are provided at some midpoints of the metallicpiping and flexibly deform in accordance with relative displacement ofeach of the pair of the hydraulic cylinders, wherein: a difference inthe relative displacement of each of the pair of the hydraulic cylinderswith respect to the control valve is absorbed.
 2. The hydraulic cylinderapparatus according to claim 1, wherein: the pair of the hydrauliccylinders are located on both sides of the driven member, and thecontrol valve and the metallic piping are placed symmetrically withrespect to a center line between the pair of the hydraulic cylinders. 3.The hydraulic cylinder apparatus according to claim 2, furthercomprising: a base plate on which the control valve is mounted, wherein:the base plate is placed between the pair of the hydraulic cylinders andis coupled to each of the pair of the hydraulic cylinders through theelastic support mechanism provided on both sides of the base plate. 4.The hydraulic cylinder apparatus according to claim 3, wherein: thecontrol valve is mounted on a face of the base plate opposite to thedriven member.
 5. The hydraulic cylinder apparatus according to claim 3,wherein: the metallic piping includes piping connected to one ofhydraulic pressure chambers of the pair of the hydraulic cylinders andpiping connected to the other of the hydraulic pressure chambers of thepair of the hydraulic cylinders, wherein: in each piping, the curvedportions are curved within an approximate right angle range on surfacesforming right angles with each other.
 6. The hydraulic cylinderapparatus according to claim 5, wherein: the metallic piping is formedby connecting a single pipe connected to the control valve and a pair ofbranch pipes which are connected respectively to the pair of thehydraulic cylinders, and the curved portion provided in the single pipeand the curved portion provided in each of the branch pipes are locatedon surfaces at right angles to each other.
 7. The hydraulic cylinderapparatus according to claim 6, wherein: the single pipe includes thecurved portion curving in a U shape, and is connected respectively tothe pair of the branch pipes on the rear face of the control valve.